As evidenced by the prior art, and the above-noted copending applications, the advantage of using size-classified toner in a xerographic device is well known.
Prior construction and arrangement for manufacturing size-classified toner has provided at least two separate means for achieving classification at the high and low ends, respectively, of the desired particle size distribution range. Thereafter, the now-classified toner was supplied to a cyclone separator whereat the toner was collected, and incidentally the very small particles were discarded as waste with the cyclone's output airstream.
The efficiency of a cyclone separator is generally defined as the ability of the separator to discharge only air as waste. The increasing presence of particles in the air-waste output of the separator is a direct measure of decreasing separator efficiency.
In the art of cyclone separators per se various means have been employed to control this efficiency, usually to maximize efficiency, or to achieve special results from the separator.
As exemplary, U.S. Pat. Nos. 3,150,943 and 3,960,734 modify the separator's top-disposed outlet tube, and the former adds clean air to minimize the discharge of dust and thereby maximize dust collection.
In U.S. Pat. No. 3,636,682 the cyclone's outlet pipe is constructed and arranged relative the inlet pipe to produce high efficiency in a dust collecting environment. U.S. Pat. No. 3,413,776 suggests that cyclone separation performance is improved by use of a bundle of tubes located within the main outlet tube. In U.S. Pat. No. 3,426,513 the length of the separator's outlet tube is required to be of sufficient length to allow a whirling air of gas column to develop, when used to filter incoming air for an internal-combustion engine.
U.S. Pat. No. 4,149,861 suggests that separation of fines from a gaseous stream is enhanced by a concentric, multi-section exit pipe of increasing length from the inner to the outer concentric pipes.
The above-noted U.S. patents are incorporated herein by reference to indicate the state of the art relative cyclone separators per se.